From: WANG Cong xiyou.wangcong@gmail.com
commit 199ab00f3cdb6f154ea93fa76fd80192861a821d upstream.
Andrey reported a out-of-bound access in ip6_tnl_xmit(), this is because we use an ipv4 dst in ip6_tnl_xmit() and cast an IPv4 neigh key as an IPv6 address:
neigh = dst_neigh_lookup(skb_dst(skb), &ipv6_hdr(skb)->daddr); if (!neigh) goto tx_err_link_failure;
addr6 = (struct in6_addr *)&neigh->primary_key; // <=== HERE addr_type = ipv6_addr_type(addr6);
if (addr_type == IPV6_ADDR_ANY) addr6 = &ipv6_hdr(skb)->daddr;
memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
Also the network header of the skb at this point should be still IPv4 for 4in6 tunnels, we shold not just use it as IPv6 header.
This patch fixes it by checking if skb->protocol is ETH_P_IPV6: if it is, we are safe to do the nexthop lookup using skb_dst() and ipv6_hdr(skb)->daddr; if not (aka IPv4), we have no clue about which dest address we can pick here, we have to rely on callers to fill it from tunnel config, so just fall to ip6_route_output() to make the decision.
Fixes: ea3dc9601bda ("ip6_tunnel: Add support for wildcard tunnel endpoints.") Reported-by: Andrey Konovalov andreyknvl@google.com Tested-by: Andrey Konovalov andreyknvl@google.com Cc: Steffen Klassert steffen.klassert@secunet.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Alessio Balsini balsini@android.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/ipv6/ip6_tunnel.c | 42 ++++++++++++++++++++++-------------------- 1 file changed, 22 insertions(+), 20 deletions(-)
--- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -972,26 +972,28 @@ static int ip6_tnl_xmit2(struct sk_buff
/* NBMA tunnel */ if (ipv6_addr_any(&t->parms.raddr)) { - struct in6_addr *addr6; - struct neighbour *neigh; - int addr_type; - - if (!skb_dst(skb)) - goto tx_err_link_failure; - - neigh = dst_neigh_lookup(skb_dst(skb), - &ipv6_hdr(skb)->daddr); - if (!neigh) - goto tx_err_link_failure; - - addr6 = (struct in6_addr *)&neigh->primary_key; - addr_type = ipv6_addr_type(addr6); - - if (addr_type == IPV6_ADDR_ANY) - addr6 = &ipv6_hdr(skb)->daddr; - - memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr)); - neigh_release(neigh); + if (skb->protocol == htons(ETH_P_IPV6)) { + struct in6_addr *addr6; + struct neighbour *neigh; + int addr_type; + + if (!skb_dst(skb)) + goto tx_err_link_failure; + + neigh = dst_neigh_lookup(skb_dst(skb), + &ipv6_hdr(skb)->daddr); + if (!neigh) + goto tx_err_link_failure; + + addr6 = (struct in6_addr *)&neigh->primary_key; + addr_type = ipv6_addr_type(addr6); + + if (addr_type == IPV6_ADDR_ANY) + addr6 = &ipv6_hdr(skb)->daddr; + + memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr)); + neigh_release(neigh); + } } else if (!fl6->flowi6_mark) dst = dst_cache_get(&t->dst_cache);